Is It Wrong to Try to Pick Up Girls in a Dungeon?! Season 4 Part 1 contains episodes 0-11 of the anime directed by Hideki Tachibana.
How low can someone go in the mammoth Dungeon of Orario and still return? With Bell recovering from his last fight, the Hestia Familia receives a mission that they can't refuse: traveling deeper into the Dungeon than they ever have before! Fortunately, missions are what friends are for, and Hestia manages to borrow a few of the Miach and Takemikazuchi Familias' heaviest hitters. Unfortunately, no one listens to Cassandra's warnings once again and things immediately start to go wrong. Now the team is split, Ryu's accused of a horrible crime, and Bell charges ahead to try clearing her name as everyone races to the lower floors.